RegExDot.Repeatable

AUTHOR

Dr. Alistair Ward

DESCRIPTION

• A data-type, which represents the permissible range of instances, of the underlying polymorphic datum.
• Designed for use in a polymorphic regex-engine, which specifies patterns composed of repeated greedy & non-greedy sequences of Meta-data;

		*	+	?	{fewest, most}	{fewest,}	{fewest}
		*?	+?	??	{fewest, most}?	{fewest,}?

• In the context of regexes, this concept is known as Quantification.
• regexes evolved from the minimal ability to optionally qualify the datum with a http://en.wikipedia.org/wiki/Kleene_star suffix. More exotic repetition-specifications could be composed by concatenating these atomic building-blocks. Here, I've taken the contrary top-down view, & assumed that all data are qualified by a full RepetitionBounds, which in most cases will degenerate into a simpler form.
• The type of entity which is being repeated, isn't the domain of this data-type; it's polymorphic.

Types

Type-synonyms

type Repetitions = Int

A number of repetitions.

type RepetitionBounds = (Repetitions, Maybe Repetitions)

Defines the bounds of a range of permissible repetitions.

Data-types

data Repeatable a

Declares a polymorphic data-type, which augments the underlying base datum, with the range of times it may be used.

Constructors

MkRepeatable

Fields

base :: a

The underlying polymorphic datum.

repetitionBounds :: RepetitionBounds

The bounds delimiting the range of permissible repetitions, of base.

isGreedy :: Bool

Whether to demand as many matching instances of base as possible; or as few (AKA lazy quantification).

Instances

Functor Repeatable

Eq a => Eq (Repeatable a)

Read a => Read (Repeatable a)

Show a => Show (Repeatable a)

NFData a => NFData (Repeatable a)

SelfValidator a => SelfValidator (Repeatable a)

Consumer a => Consumer (Repeatable a)

Constants

oneOrMoreToken :: Char

The token used to denote oneOrMore, when in the String-form.

rangeDelimiters :: (Char, Char)

The delimiters of ^#->#, when in the String-form.

rangeSeparatorToken :: Char

The token used to separate RepetitionBounds, when in the String-form.

tokens :: String

The set of Char to which a specific meaning is attributed, when reading from String.

zeroOrMoreToken :: Char

• The token used to denote zeroOrMore, when in the String-form.
• AKA Kleene Star.

zeroOrOneToken :: Char

The token used to denote zeroOrOne, when in the String-form.

Functions

one :: a -> Repeatable a

• Construct a Repeatable, tailored for unrepeated data.
• A degenerate case of ^#.

oneOrMore :: a -> Repeatable a

• Construct a greedy Repeatable, from a polymorphic datum, with lower RepetitionBounds == one.
• A specific case of ^#->.

oneOrMore' :: a -> Repeatable a

Construct a non-greedy version of oneOrMore.

zeroOrMore :: a -> Repeatable a

• Construct a greedy Repeatable, from a polymorphic datum, with fewest == 0.
• A specific case of ^#->.

zeroOrMore' :: a -> Repeatable a

Construct a non-greedy version of zeroOrMore.

zeroOrOne :: a -> Repeatable a

• Construct a greedy Repeatable, from a polymorphic datum, with fewest == 0 & most == 1.
• A specific case of ^#->#.

zeroOrOne' :: a -> Repeatable a

Construct a non-greedy version of zeroOrOne.

repeatableParser :: a -> Parser (Repeatable a)

Builds a parser for a specification of the number of permissible instances of the specified polymorphic parameter.

showSuffix :: Repeatable a -> ShowS

• A ShowS-function for the suffix, denoting the permissible repetitions, of base.
• This function converts the internal, into the tradition greedy & non-greedy quantifiers of various specific varieties.

Accessors

getFewest :: Repeatable a -> Repetitions

Accessor.

getMost :: Repeatable a -> Maybe Repetitions

Accessor.

Mutators

focus :: Repeatable a -> Repetitions -> Repeatable a

Reduces a Repeatable, with a range of RepetitionBounds, to a precise number of repetitions.

toSingleton :: Repeatable a -> Repeatable a

• Reduces a Repeatable, with a range of RepetitionBounds, to a singleton.
• A degenerate case of focus.

Operators

(^#->#)

Arguments

:: a

The polymorphic payload from which to construct the Repeatable.

-> RepetitionBounds

The permissible repetition-bounds for the polymorphic data.

-> Repeatable a

• Construct a greedy Repeatable, from a polymorphic datum, with the specified range of permissible instances.
• The #s in the identifier represent the two bounds.
• a{f, m}

(^#->#?)

Arguments

:: a

The polymorphic payload from which to construct the Repeatable.

-> RepetitionBounds

The permissible repetition-bounds for the polymorphic data.

-> Repeatable a

• Construct a non-greedy version of ^#->#.
• a{f, m}?

(^#->)

Arguments

:: a

The polymorphic payload from which to construct the Repeatable.

-> Repetitions

The minimum permissible repetitions of the polymorphic data.

-> Repeatable a

• Construct a greedy Repeatable, tailored for data repeated at least the specified number of times.
• The # in the identifier represents the single bound.
• a{f,}

(^#->?)

Arguments

:: a

The polymorphic payload from which to construct the Repeatable.

-> Repetitions

The minimum permissible repetitions of the polymorphic data.

-> Repeatable a

• Construct a non-greedy version of ^#->.
• a{f,}?

(^#)

Arguments

:: a

The polymorphic payload from which to construct the Repeatable.

-> Repetitions

The precise number of repetitions of the polymorphic data which is required.

-> Repeatable a

• Construct a Repeatable, tailored for data repeated a precise number of times.
• The # in the identifier represents the single bound.
• a{f}

Predicates

isPrecise :: Repeatable a -> Bool

True if there's no choice in the number of repetitions; implemented via isPrecise.

hasPreciseBounds :: RepetitionBounds -> Bool

Predicate which is True if exactly one value is permissible, ie lower & upper bounds on the number of Repetitions are identical.